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Principles of Physiology

by: Eusebio Dare PhD

Principles of Physiology ZOO 3103

Marketplace > University of Oklahoma > Animal Science > ZOO 3103 > Principles of Physiology
Eusebio Dare PhD
GPA 3.65

Bing Zhang

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Bing Zhang
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This 100 page Class Notes was uploaded by Eusebio Dare PhD on Monday October 26, 2015. The Class Notes belongs to ZOO 3103 at University of Oklahoma taught by Bing Zhang in Fall. Since its upload, it has received 10 views. For similar materials see /class/229242/zoo-3103-university-of-oklahoma in Animal Science at University of Oklahoma.


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Date Created: 10/26/15
Princip gg Lecture 2 Resting amp Action quot Potentials part I Today s goals sEquilibrium and resting states How they differ from each other sNernst and GoldmanHodgkinKatz GHK equations Neurons are specialized cells Neurons and muscles are electrical excitable cells in animal bodies because they produce Action Potentials APs APs are transient expression of membrane potentials mediated by specific changes to ion permeabilities Basic properties of APs sComputer simulation of resting potential and APs 10 mV 150 mV VmJlmV Predicted Vm 81 mV 5 mM 100 mM K Why Multiple Ion Permeability amp Membrane Potential RT PK K0 PNa Nao PCl Cui Vm ln F PK KL PNa Nai PCl Cuo When a cell membrane is permeable to K as well as Na and Clquot simultaneously membrane potential can be determined by an equation called Goldman Hodgkin Katz GHK Equation Note that ClO and Cli are reversed in this equation because Z for C1quot is negative one 3 GHK simpli ed RT PK KL PNa Na0 Pc1 C111 Vm 11 1 F PK Ki PNa Nai PC1 C1O KO b NaO C C1i Ki b Nai C C1O 5810g b PNaPKz 002 c PClPK 00001 A realistic resting membrane potential Na 120 mM K10 b Na0 Ki b Nai 5 002 X 120 125 002 X 12 K SmM 39 7 r 39 12524 71mV 05810g 5810g Key Features of Resting Potentials 1 Select and different permeability to more than one ions 2 Uneven distribution of ions are still needed 3 No equilibrium state is ever achieved for any of the permeable ions These ions negotiated a peaceful coexistence deal to live with only one membrane potential resting potential Whoever that has the highest permeability has more say on the resting potential ie Vm close to its Eion To maintain chemical gradients ATPconsuming NalK pump is needed Neuron S rr39uc rur39e and Func rion Neurons are not all alike they vary in structure and properties Use the same basic mechanisms to send signals Sensory neurons Inlerneurons of CNS Efferent neuron Neurons for smell and vision 7 L Dendritesi l Somatic senses Schwann 39 cell Axon Axon De nd rites Dendrites l quot Axon 4c Axon lerminal Pseudounipolar Bipolar Anaxonic Multipular a h c Copyright 2009 Pearson Educallon inc 9 The Nobel Prize in Physiology or Medicine 1906 quotin recognition of their work on the structure of the nervous system N a camqu Golgi 1 12 of the prize Italy Pavia University Pavia Italy D 1843 d 1926 Santiago Ramon y Gain 1 12 of the prize Spain Madrid Universuy Madrid SDaln D 1852 d 1934 i ii 3 I v i u 1 3 3 Kt quot httpnobelprizeorgnobelprizesmedicineIaureates1906indexhtm g Examples of differem ly shaped neurons Pu39ki le Parallel 05 cells the r39 392 Molecular layer Slellale cell Ascending branch of Gigglellar granule cell axon I nary layer Recurrent collaterals Basket 39quot Cnmbmg liber Mossy llbu Purkinje axons httpCsnbeckmanuiuceducerebellumgif There are four functional neural zones 1 Signal reception dendrites and cell body soma Incoming signal is received and converted to a change in membrane potential 2 Signal integration axon hillock Strong signal 9 action potential AP 3 Signal conduction axon some wrapped in myein sheath AP travels down axon and to backward to dendrites too 4 Signal transmission axon terminals Neurotransmitter is released Functional zones of atypical neuron Input Dendriles signal 1 L 7 l 32E K k 4 W inhalation l G iv w if KNuclgls f Axon hilluck Cell 7i body 4 l Axon initial segment i l i Myelin l h in k j 5 ea iCL H k Presynaptic ll axon terminal x V u i t4 i i 39 quot Output i signal Synaptic Synapsen cleft 343 1 Postsynaptic i C L dendrite 7 Postsynapiic fx neuron fl 3 i l ll Copyright 2009 Pearson Education Inc Change iS good Membrane potentials can change dramatically in neurons amp general terms used to describe these changes Depolarization Repoiarization Repolarization Resting membrane Hyperpolarization potential Membrane potential mV Time msec Copyrighi 2006 PeaISacn Education Incl publishing as Benjamin Clummngs What will occur to a resting potential if there is sudden increase in a PM or b PM Whenever given a chance ie increase in permeability the permeable ion will always try to bring the membrane potential to its own equilibrium potential Because no neurons are permeable only to a single ion an equilibrium state will never be reached you may consider it a dream for the ion not the reality This is a key concept on membrane potentials including action and synaptic potentials Membrane potential mV Ion permeability Resting membrane potential Depalarizing stimulus 0 Membrane depolarizes to threshold in n z m In E to a n E 39u m a A Rapid Na entry depolarizes cell Na channels close and slower K39 channels open I G 9 0 K moves from cell to extracellular uid E C G D K channels remain open and additional Kquot leaves cell hyperpolarizing it Voltagegated K channels close less K leaks on at the cell Cell returns to resting Inn permeability and resting membrane potential Threshold D 2 3 4 Time tmsec gt Resting RisinglFaiiingl Resting l Iquot l Voltage lNa39 l l 1 t r i gt V V gt V V n 1 2 3 4 Time msec e Copyright 2009 Pearson Education lnc The Action Potential Life Will be boring to death in fact dead Without action A B C potentials VSO how to get an action potential and how is it generated The Nobel Prize in Physiology or Medicine 1963 quottor than ul5nirt39erir3 I rruerr39m39ng the Izmir matl iar ner39rts Ir39r 39n39 enl In ai 39n39rtatlon and Intuinitmur39r m the peripl39reral and central Hartman or the HEPSE call i39narnbrane For their discoveries concerning the ionic mechanisms involved in excitation and inhibition in the peripheral and central portions of the nerve 99 Sir John Carew Alan Lloyd Andrew Fielding CCii membrane Eccles Hodgkin Huxley O O 0 Australia Great Britain Great Britain Australian National Cambridge London Ur uiuersitlI University UniversityI London Great Canberra Australia Cambridge Great Britain Britain 1903 1997 1914 199B 191 Basic Properties of the Action Potential 1 It is transient The duration of an AP is usually less than 1 ms 2 It is an allornothing event hence it is voltagedependent Threshold L r 3 It propagates along axons at rates ranging from 5 ms to 100 ms and can back re to cell body and dendrites 4 It has refractory periods Threshold for AP production Triggered by the net graded potential at the axon hilock trigger zone Must reach threshold potential to fire hence it is all or none Sublhmshum 4 dnpallrlmtlon theshuld poterulal Heinng quotimmune potenltal Membmne poi ai mm L I 2 s 7 3 1 mimm ii Subthreshold graded potential h or E 10 V g or 3 5 4 mmmm 2 6 quotTITquot 39quot39E quotE39 quot3quot 39 Resllng mummann pntwnilal 4m i 2 a a 5 s 7 i mm Li I Suprathreshold act on potential Refractoriness of APS Relative refractory period Absolute refractory 39 period Stimuli Refractory periods Absolute refractory period incapable of generating a new AP upstream Na channels inactivatedmembrane must repolarize so channel proteins can return to openable state Relative refractory period more difficult to generate a new AP some Na channels still inactive and increased K channels are open The ionic basis of the action potential A B C E 5 40 40 40 33 Control LOW Na Recovery 3 0 0 0 g 40 40 A 40 5 80 8O 80 05 0 1 2 3 0 1 2 3 0 1 2 3 2 Time ms Unlike the resting membrane potential AP is highly dependent on the extracellular Na Hodgkin amp Katz 1949 http MNva cbl mm mm govbooksbv fogi7r1dneurosci TOCampdeplh2 Neuroscience by Purves et al A Lethal War Between A Bullfrog and A Newt Tetrodotoxin TTX one of the most potent toxins in nature I am deadly goodlooking 915 Ho quot390 H H 0 HzN OH H 2 HO J H DH httppuffernettripodcoma p html N0 TTX TTX Wash n n n Anatomy of the AP dynamic interplay between N a and K currents EN 58 mV a PNaft PM OrnV 70 mV 80 mV Electrical Equivalent Circuit Outside ENa 58 mV quot ENa BK l i J v EK 81 mV 1 J Inside Oh 1 I ion G V m s aw Driving force VIR IG G VmEan Hence I Challenge How do you express Vm using Ohm s law Make sure to do these before coming to the lecture Visit pages 38 50 and 58 and do the homework and prepared to answer questions On page 38 you are assigned a case study see the video posted on the Links on D2L Laugh and learn A brief visit of the syllabus and grading policy GRADING Course component Poin rs Quizzes 200 Exam 1 100 Exam 2 100 Exam 3 100 Final Exam 100 TOTAL 600 GRADING SCALE 390 8070398970 7070397970 60706970 The r39es r 39HUGW Chances To earn 39extra credits Yes Tips for Success gt Read Tex r before coming T0 class gt Lis r a few key ques rions and Try To answer Them Google if necessary gt Come T0 class InTro Zoology spoTchecks showed Grade Modal Average Grade Always a r rended class 80 A Did no r a r rend class 65 F Tips for Success gt Read fexf before coming fo class gt Lisf a few key quesfions and Try To answer Them Google if necessary gt Come To class gt Ask ques rions in class or during office hrs gt Keep a nea r no rebook rewri re no res Expand on PowerPoin r no res gt USE OFFICE HOURS no r jus r righ r before exams Multiple Chances for You to See US Each Week Instructor Dr Bing Zhang Friday 11 am12 noon amp 24 pm Or by appointment Teaching Assistant TA Teaching Assistant TA Rachel Hein Alexandra Wilson Tuesday 430530 pm Thursdays 430530 pm Richards Hall 250 Richards Hall 250 Tips for Success gt Read fexf before coming fo class gt Lisf a few key quesfions and Try To answer Them Google if necessary gt Come To class gt Ask ques rions in class or online gt Keep a nea r no rebook rewri re no res Expand on PowerPoin r no res gt USE OFFICE HOURS nof jus r righf before exams gt Tes r yourself periodically Tests improve Retention 53 I Study Study Study Test 53 I a c Prapomnn of Idea Unns Recalled a 5 Minutes 2 Day 1 Week Relemiun lntarva Roediger and Karpicke 2006 PsychJSci Tips for Success gt Read Tex r before coming T0 class gt Lis r a few key ques rions and find answers gt Come T0 class gt Ask ques rions in class or39 online gt Keep a nea r no rebook r39ewr39i re no res gt USE OFFICE HOURS no r jus r r igh r befor39e exams gt Self res ring gt Farm s rudy groups Teach each o rher39 gt Use efficien r s rudying meThod spaced vs massed learning 11 Spaced Learning vs cramming Retention Psychology of Study by Prof C A Mace 1932 ORepetitio est mater studiorum repetition is the mother of learning OCramming before an exam is not a good idea12 Tips for Success gt Read TexT before coming T0 class gt LisT a few key quesTions and find answers gt Come T0 class gt Ask quesTions in class or39 online gt Keep a neaT noTebook r39ewr39iTe noTes gt Use office hr39s noT jusT r39ighT befor39e exams gt Self TesTing gt For39m sTudy gr39oups Teach each oTher39 gt Use efficienT sTudy meThod no cramming gt Explain The figures in The Tebeookpower39poinT lecTur39e aloud To your39 friend your39 dogcaTfish The wall or39 even a fooTball Any questions about the syllabus and grading policy Who r is Physiology Under39s rond how animal bodies wor39k Through i n rer connec red molecules Tissues and organ sys rems 5533quot v Our general goals 1 IdenTify The imporTanT sTr39ucTures in The various animal organ sysTem and describe Their39 funcTions 2 Explain how These differenT organs work TogeTher aT cellular molecular and sysTems levels 3 PredicT how each organ sysTem will aITer39 iTs funcTion in response To a specific perTurbaTion 4 Explain how specific i nTeracTions beTween sysTems can a increase The probabiliTy of survival or reproducTion b cause heaITh problems And having fun while learning TogeTher 16 Overall plan for The semes139er39 logic behind syllabus Main concest and players Common con rrol mechanisms Specific organ sys rems Levels of Animal Organization and Analysis Organismal I physiologists 77 A Organism Cellular and molecular l physiologists mgmysm f 1 Systems Maiacuiu with a physiologists o I x 1 Developmental physiologists Evolutionary Ecological W s mm En VIronmental Ecusynlems alnspnem Cwlwm c eons Pamquot szlmn m mamW as Humani Cuminv1 Cummunllles Levels of Animal Organization and Analysis Physics tool PHYSIOLOGY ECOLOGY CELL MOLECUIAR B39 L GY CHEMISTRY Elm05V Organ Populations of Ecosystem of a a a A dinerem Speaks Bmsphem Copyright 2009 Pearson Education inc Unifying Themes in Physiology Physiological processes obey physical and chemical laws Physiological processes are usually regulated Homeostasis maintenance of internal constancy Physiological phenotype is a product of the genotype and the environment Genotype genetic makeup Phenotype morphology physiology and behavior Genotype is the product of evolution Natural selection Genetic a rift e g founder effect What we39re studying This semester Genotype Adult Phenotype Molecules v Gills DeveloE b Tissues r DPhysiology Reproduction A i and A A bohavior Organs Organ systems Environment Random Natural processes sanction Copyrighl 2006 Pearson Education Inc ptblishmg as Benjamin Cummings 1 39 1 Physiological Regulation Strategies for coping with changing conditions 0 C onformers allow internal conditions to change with external conditions e g an iguana and other ectothermi animals Hea amp Hcauamp on 0quot Regulators maintain relatively constant internal conditions regardless of V external conditions 0 100 200 300 400 500 endothermic animals Timelm39quot Body temperature C O Figure 14 The relo rive cons roncy of The in rernol environmen r is called HOMEOSTASIS homeo similar sfasis condi rion IT is THE major principle underlying physiology IT is involved in vir ruolly every process we will discuss This semes rer 23 Mechanisms for Changing Levels of a Parame rer in Body A Nega rive feedback B Posi rive feedback C Feedfor39war39d r39egula rion 24 A NegaTive Feedback 1 Major mechanism for39 main raining homeos rasis 2 Thermos ra r is classic example eg air conditioner main rains Tempera rur39e a r designa red se r poin r 25 Re mated variable Sensors lnlagvming Dame Thermostat Elfecmrs Mme Panmn Educamn m yumsmw as mm Uummms A Nego rive Feedback 1 Major mechanism for39 moin roining homeos rosis 2 Thermos ro r is classic example 3 Terminology sligh rly different in physiology 27 SensorRecepfor senses how much of some rhing is presen r or is produced eg Thermorecep ror pho rorecep ror hormone recep ror Effecfor produces a response eg muscle gland Infegrafing cem er collec rs informa rion from many sys rems usually brain 28 Regumed variable Sensors lnlagvming name Bram mermoregmmry cemevs compare acmal smparamrs h 551 pom and sand appmprlaw slgna s lo a edors Nnrmal body lemperamra Body empamura Emma 2092 Panme Educamn m gumsMasnenmmcummm Body Body emparamrs lemperalurs rises acl39va ed analslgnal increases decvezses E Enov X 5 na E g g 2 37 Set pnim nnrmah m Tune d mama Pearson Eamon m WMISMVUE Bamvmn 01mmst Your body as o Thermos ro r Moin roins vorie ry of measures of por riculor levels sef poinfs body Tempero rure blood sugar 02 COZ wo rer levels of hormones recep rors cholesTerol ro re of cell division and cell deoTh gene expression enzymes pro reins blood pressure sTomoch ocidiTy 31 Bu r se r poin rs can change 39 fever daily rhythms of body Temperature lower a r nigh r 32 A NegaTive Feedback in rernal change a reac rion a s rabiliza rion of parame rer VW Time minutes B Posi rive Feedback in rernal change a reac rion a exaggera rion of parame rer 33 B Posi rive Feedback in rer39nal change a reaction a exaggeration of parameter does NOT main rain homeos rasis by i rself bu r s rill ver39y impor ran r when if occur39s good or39 bad blood clo r ring ac rion po ren rials Ovula rion inflammation 35 C Feedforward Regula rion An ricipa res changes in a regula red variable eg a cruise con rrol sensor Tha r 39de rec rs39 The approaching of a hill eg STomach produce HCI in par ricipa rion of food eg Why doesn39T body Temp fall when you go ou rside in win rer Tempera ruresensi rive nerve cells in skin as well as cen rral neurons regula re body Tempera rure 36 Equilibrium and Resting Potentials Major goals Electrical potentials as a common physiological currency for all living cells Take charge of cell membranes ions channels and equilibrium potentials 37 You ume Imens Channels Shaw Fainting Goats l a 7 7 p kus w a Case Study 1 What does a fainting goat tell us about ion channels and membrane potentials Guidelines 1 Before you read anything from the internet What hypothesis will you make based on the behavior of the fainting goat 2 How Will you experimentally test your hypothesis also see Links on D2L 38 Biological Membranes As Ion Selective Barriers 0 59 9 V charged and i hydrated ions to e J09 ooowoeg J pass through lecnhnid Fquot Fortunately Some of these transmembrane proteins function as ion selective channels Imuq pgauaqmua my uvl 1 7 1 nldnauusmu an N I mvmlic pul na ION CHANNEL More on ion Channels in later lectures The Electrodiffussive Nature of Bioelectricity Neuronal communication depends on changes of membrane potentials Neurotransmission differs from electricity in that signals are not transmitted down nerve bers like current travels down a metal Wire i e at the speed of light Electricity is carried by mobile electrons in the metal Wire Neuronal signals are carried by charged ions from dissolved table salts eg NaCl and KCl in our body water takes up 75 WW gt99 of molecules The maX speed is about 120 meters sec 260 mph Animal electricity is generated by diffusion of ions from these salts blew 1 Basic Properties of Diffusion Solutes charged or noncharged always move from a higher concentration to a lower concentration This movement Will eventually stop When a uniform concentration of solute is formed throughout the solution In other words the movement reaches an equilibrium such that movements of the solute are the same in all directions O O O O 03 O O O O o o o 0 T20 T2hrs Diffusion Across Membranes Initial Equilibrium mM mM gt K Cl39 10 mM 55 mM KCl KCl Although there are transient Equally Permeable to diffusion potentials 0 K and Cl equilibrium potential is established across the cell 43 membrane How to achieve a negative equilibrium potential permeable only to K 10 mM KCl Just say No to Cl It should be clear from our example that diffusion alone is insuf cient to establish a potential difference PD across a cell membrane A PD can be achieved if we make the membrane selectively permeable only to one ion eg K but not to another e g C1quot in this simple model 44 Initial conditions Equilibrium V insideoutsiode v 10 mM KCl 45 V2 At equilibrium 10 mM KCl Only K moves across the membrane BK RTZF 1n KOKi 58 mVZ 10g KO 1011 Note RTF 58 mV 20 C EK 58 mV1 10g 10100 58 mV 10g 01 58 mV Inside is negative 49 At equilibrium A Quick Quiz What is EC Which side of the 10 mM m membrane IS more negative Answer this quiz before coming to the class 50 Naturally EK Will be zero if the KCl concentration is msmneonbmhskbso henmnmmme At equilibrium K VOn1V 100 mM KCl Thus chemical gradient and selective permeability are both important One cannot have Niagara Falls in ourflat but yet beautiful Norman 51 Summary of the Equilibrium Potential The equilibrium potential speci es the amount of electrical gradient voltage required to exactly balance a given chemical gradient potential across a semiselective membrane It takes only minor separation of a charged ion to establish an equilibrium Thus there is no signi cant change in ion The equilibrium potential for a permeant ion can be calculated using the Nernst equation At equilibrium the permeant ion is passively distributed across the membrane That is the ion is in complete harmony With its electrochemical environment requiring no metabolic energy At equilibrium ions move in and out at an equal rate such that the net movement is zero 52 ZOO 3103 Principles of lquot 794 Spring to Lecture 5 AP Propagation stsLongdistance signaling Propagation of APs and strategies stsAxon size matters stsGlial cells as partners of neuronsmyelin stsThe biophysics of AP propagation otsLength constant and time constant APs are not unique to neurons or muscles some plants can produce APs although slow Propagation of the Action Potential A F J A 0 l B 9 Q n n l n 6 ga 65 le quotl39 V IV 2 02468024680246802468024680246802468 CL ms 4 P 4 httpmmwncbinlmnihgovbookslbvfcgiridneurosciTOCampdepth2 Neuroscience by Purves et al How a local circuit is generated Local current flow Depolarized section ofaxon Copynght 2009 P eeee on Education Inc Local Circuits and Current Flow During A Nerve Impulse v Trigger zone 39 A graded potential above threshold reaches the trigger zone Axo n 39 K39V Copyright 2009 Pearson Education Inc Voltagegated Na channels open and N211 enters the axon Copynghl 2009 Pearson Education Inc Local Circuits and Current Flow During A Nerve Impulse v Positive charge flows into adjacent sections of the axon by local current flow V Copyright 2009 Pearson Educatlon inc Local current flow from the active region causes new sections of the membrane to depolarize l 7 quot V J A A quotquot39quot quotquotquotquotquotquotquotquotquotquot39 j VK Refractory Active region I Inactive region region 39 I Copyright 2009 Pearson Education inc Local Circuits and Current Flow During A Nerve Impulse 4 Local current flow from the active region causes new sections of the membrane to depotarize mh h A V Vk E Refractory I Active region Inactive region region Copyright 2009 Pearson Education inc 11 quot V V The refractory period prevents backward conduction Loss of K from the cytoplasm repolarizes the membrane RD I Refractory Active region Inactive region region Copyright 2009 Pearson Education Inc AP Propagation One way and the only way 6 9 Electrodeshagligiir J WNWMM I I I I I Direction of conduction gt V Membrane potential mV I I I I l I I I I II I I I I I I I I I I I I A Membrane potentials fl recorded simultaneously from each electrode 3 I 39I 39I Time a Copyright 2009 Pearson Education Inc Revisiting Na Channel Inactivation Na and K channels If quotIllll ll Lillih u o i R 9 Both Na 139 I 39 Both channels channels Na channels cl e and Na channels reset to original position channels closed pen K channels open while K channels remain open c used 1mm 30 30 Absolute refractory period Action potential V N Relative refractory period E E v39 a g Why did I cross close out s g Q E 2 What IS wrong with the a m 5 statement 239 E 2 a E E High High E g Increasing U K Lu Zero l 1 0 1 2 II 4 Time msec Copyright 2009 Pearson Education Inc A Spring Model of Resting and Action Potentials Resting Peak of An AP ENa Vm Omv gt Vm EK Strategies for AP Propagation 1 The larger the axon the faster the AP Nerve lmpulses reach me muscle a many mulls m um manna canny Why size matters Need to consider passive ow of current and cable properties A Axon G 1 if J H B QCEME RIM QM gm Rm imam ism 3 OJ g 59 395 E 62 g5 65 n 25 O 20 400 20 400 20 400 20 400 20 400 20 400 20 40 Time ms C 50 Threshold 55 60 6r Resting potential 05 0 05 10 15 20 25 Distance along axon mm httpmMANncbinmnihgovbooksbvfcgiridneurosciTOCampdepth2 Neuroscience by Purves et al Revisit Electrical Equivalent Circuit ENa 58 mV Outside C ENa E6 Vi 5 BK 81mV Gvnf IionzGV Driving force Eion l l Inside Ohm s law VIR IG Hence I VG Resistance to Current Flow in An Axon The role of membrane capacitors Point C Cable axon geometry and membrane tightness determine the length constant Distance from current injection mm The length constant A is the distance where the initial voltage decays to l e 37 You may consider it the stepquot anAP can make When walking On an axon hftp39lmAwxl n r hi nlm quot 39 39 39 r Neuroscience by Purves et al Why size matters S S E I I 1 1 quotMenus M x quotmrznsxs m I I I I 4 5 Ixxxmxw quotriwsxsxs zsn A a a I I m u l h E h 25 5 nee rum a 5 muusImm an sax anwmm Mum mawmmmw Aquot V 39A 5 Alarger axon has a longer length constant Arr 07 hr LE t S enabling an AP to exct neighboring site further downstream WWWpnmmm mmanmcwmu Fig 525 Fig 521 Strategies for Nerve Impulse Conduction 1krm rm rir0 ri 1 Increase axonal diameter Will decrease ri thereby increasing k 2 Insulate the axonal membrane Will increase rm leading to a longer 9 Equivalent Pathway of Current Flow Impact of Straw Properties on Coke Drinking f holes lt 0 N kf 9 Gait V are V When the same suction is applied how much coke one can drink depends 0n 1 The diameter d of the straw Which in turn determines hOW easily cokes ows iethe internal resistance 1 lt F 2 The tightness membrane resistance rm of the straW wall r Qlt 1 m leakmess 3 Overall ow rm Coke Qlt T l Varieties of neuroglial cells A Astmcyte B Oligodendmcyte C Microglial cell Cell 1 body Glia l processes Glia A Astrocyte B Oligodendrocyte C Microglial cell pI OCBSSES gt 1 Called Schwann CNS Found only in the CNS iebrain and cells In the scaVenger cells peripheral nervous spinal cord Systems Glia cells are not passive supporting cells hffp39 2mm med mm Strategies for AP Propagation 2 Wrap it up with myelin and force a longer length constant NNNNN a nnnnn ar aaaaaaaaa D2095 mymsmum ln unhmwu mmmmm Fig 514 Myelin sheets are biological insulators of mammalian axons Distinctive arrangement of cytoskeletal elements in neurons The Node of Ranvier is the hot spot for AP Production V gated Na channels V gated K channels Vgated K channels A Myelinated axon Node of OOligodendrocyte 3 Ranvier 39 Myelin sheath Vgated K Channels Vgated K channels WWW jpg Vgated Na channels SaltatorV Propagation of APs Alongy a MVelinated Axon Node Node 0 9 Node of Ranvier Myem Sheath l i illl ill i39 e 4 i a Action potentials appear to jump from one node of Ranvier to the next Only the nodes have Na voltagegated channels Degenerated myelin sheath a l quotI 777777777777 7 H Na Current leak 2 slows conduction 39 A l 739 H l l li nl mi gi l i in m7 rm w l t 7 r r r r r r r r r r r r r r r n 7 7 7 V 7 7 7 V H b 4 39 39 4 39 39 L we previously insulated regions between the nodes Copyright 2009 Pearson Education Inc Multiple sclerosis MS is caused by demyelination and axonal in ammation in the CNS What is an AP for Information transfer AP frequency carries information AP frequency increases with stronger stimuli Maximum frequency is limited by absolute refractory period Mammals 500 1000sec one smart pmanhal E i an i 3 40 g sn E qt 2 wt 9 Q suhmmshald Erlet Sustnlned sltmulus quottreslmld threshold stimulus sllmulus A weak sttmutus lrlggsrs a tow1requumy o acttun woieniwls Membrane potential mVl Figure 515 Sustnlned Sustained tmugnum sunrammshuld stimulus sumulus ID A supratmesttotc stimulus uggsvsa mun lwquency at anllnn patentlals Different Faces of Action Potentials Skeletal muscle 400 U 30 mSec Cardiac muscle U lOmV I R mm 400 mmquot quot D 100 200 300 mSec Memb rane potential will 2mm m1 my M Electrics seeskrug A O lulle39mml ll l lltlll Q G39Ulillllrflll 39 damn pvltg39lc 39Ialy39u39l aquot P 9 U Acetylm me M Time Ls lug rllv Kl l Mquot l 7H l u V 5 mV 7 l l t Ullzlll 39 gt I39 ll N in F l L 3 J k 39 39 m quot quotarr 1U m M fllll ll F A quotquotr 2 I10 mv W v LP Kw lmmv WW IC wL nu PY inl 05 SEC Even plant cells use APs in cellular signaling TM Jam stil r ltnnnrgra tintn Naurrrsnmm Emaain t iJJNl ji hall F307 11M AERA Action Potentials in a Giant Algal Cell A Comparative Approach to Mechanisms and Evolution of Excitabillty Bruce R Johnson Robert A Wyttenbach Randy Wayne2 and Ronald R Hoy Departments at Wenrobwlogy and Behavior 86 Mudd Half and Pr39ant Biology Plant Sciences Bui ding Cornet39 University lthaca N Y 148501 The giant alga Chara coratiina generates action potentials Al s 39n response to mechanical stimulation injury or dll39BCl electrical stimulation Students examine the wavetorm characteristics at these AF s using standard Intracellular recording techniques lntrawllular recording is easier than with neurons because at the large sue oi the Chara cells Students observe very negative resting potentials up to 250 mV large AP amplitudes With depolarizing peaks approaching 0 mV AP durations at seconds and refractory periods up to several minutes Students calculate Nernst potentials for the ions distributed across the Chara cell membrane to hypothesze the ions responsible tor the resting potential and for the depolarizing phase at the AR These calculations suggest that K is responsible for the resting potential and that Caquot influx and Caquotactrvated Cl39 elflux are responsrble tor depolarizing phases of the AP which they are Cumpanson of the Chara AP characteristics Wlth animal neuron and muscie APs reintorces understanding of mechanisms at exclaoilily in animals demonstrates that multiple solutions exist for action potential generation and leads to discussion of the evolution ol ion channels and excitability Key words action potential Chara excitability evolution


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StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.